1. Field of the Invention
The present invention relates generally to fastening devices and, more particularly, to ratchet buckles, strap tensioners, cargo retraining devices and the like for tightening and tensioning straps.
2. Related Art
Ratchet buckles, also commonly referred to as cargo restraining devices and strap tensioners are commonly used for tightening and securing straps, ropes, chains or other tie-down tensioning lines. Generally, conventional ratchet buckles include a ratchet mechanism and a securing mechanism for retaining the strap in a tensioned condition. Conventional ratchet buckles for tightening and/or tensioning straps are described, for example, in U.S. Pat. Nos. 2,889,136, 4,185,360, 4,227,286, 4,199,182, 4,324,023, 4,570,305, 4,542,883, 5,282,296, and others.
Although such ratchet buckles are quite effective in tensioning straps, there are a number of drawbacks associated with using conventional ratchet buckles under certain circumstances. One such drawback of is that a limited length of the lashing strap is wrapped around the drum or reel of the ratchet buckle in response to a single tensioning operation. As a result, a large number of tensioning operations must be performed to uptake lengths of the lashing strap. This oftentimes requires significant time performing numerous manipulations of the ratchet buckle.
Another drawback manifests itself when the conventional ratchet buckles are secured and fully tensioned, restraining a load under a tensioned lashing strap. It is often difficult to release the tension on the lashing strap to remove or adjust a secured load. As a result, fragile loads are sometimes damaged in the process of loosening or de-mounting the lashing strap and ratchet buckle.
What is needed, therefore, is an apparatus that enables an operator to quickly and easily adjust a lashing strap when performing tightening/securing and loosening/releasing operations with a ratchet buckle.
The present invention is a ratchet and cam buckle tensioning assembly, interposed between a lashing strap tensioned by the ratchet buckle and a lead strap tensioned by the cam buckle. The tensioning assembly enables an operator to quickly and conveniently pre-tension the lashing and lead straps by removing an un-tensioned length of the lead strap without having to operate the ratchet buckle. This advantageously enables the operator to utilize the ratchet buckle to tension the straps only when the requisite tensioning force cannot be provided by an unaided operator. That is, the ratchet buckle may be operated only to tension a lashing strap that has been pre-tensioned with the cam buckle, thereby facilitating the use of the combined assembly. As a result, the present invention saves an operator from having to operate the ratchet buckle multiple times to uptake slack in the lashing strap when the leveraged tensioning force provided by such a ratchet buckle is unnecessary.
In one aspect of the invention, a tensioning assembly for tightening and releasing a lashing strap and a lead strap is disclosed. The tensioning assembly includes a ratchet buckle for tensioning the lashing strap in stepped increments and a cam buckle for slidingly adjusting the lead strap. The cam buckle is connected adjacent to the frame member by an apparatus other than the lead and lashing straps. The ratchet buckle may be any known ratchet buckle. In one embodiment, the ratchet buckle includes a bifurcated frame member having a pair of opposing parallel arms between which a reel member and ratchet wheels are rotatably mounted. A latching plate is also slidably mounted between the arms for latching the ratchet wheels when the ratchet wheels are not being rotatably driven. The ratchet buckle also includes a lever member rotatably mounted on the reel member and having a pair of opposing side members between which a ratchet drive plate is slidably mounted for engaging and driving the ratchet wheel when the lever member is actuated.
In one preferred embodiment, the cam buckle housing and the ratchet buckle frame member are a unitary member, forming an single, integrated tensioning assembly. In another preferred embodiment, the cam buckle is permanently attached adjacent to the ratchet buckle. In one particular embodiment, the cam buckle is attached to the ratchet buckle with an intermediate strap. In this embodiment, the ratchet buckle frame member includes a first cross bar supported between the pair of opposing frame member arms, and the cam buckle includes side members attached to opposing sides of the pressure plate with a second cross bar supported between such side members. The intermediate strap is fixedly connected to the first and second cross bars, and is of such a length so as to place the cam buckle adjacent to the ratchet buckle.
In an alternative embodiment, the cam buckle includes a housing adapted to slidably receive the lead strap. The housing has a pressure plate with a first restraining surface over which the lead strap slides. Also included in the cam buckle is a pawl movably mounted to the housing. The pawl has a second restraining surface and is biased in an engaged position to restrain the lead strap between the first and second restraining surfaces so as to prevent movement of the lead strap in one or both directions. The pawl also may assume a disengaged position wherein the lead strap can move freely between the first and second restraining surfaces. In one embodiment, the cam buckle is unidirectional, preventing movement of the lead strap a single direction. Particularly, the pawl, when in the engaged position, prevents movement of the lead strap in a direction that loosens the lead strap while allowing movement of the lead strap in a direction that tensions the lead strap. In one specific embodiment, the housing has a rear portion facing toward the ratchet buckle and a front portion facing away from the ratchet buckle. The lead strap travels from the front portion to the rear portion of the housing to tension the lead strap and from the rear portion towards the front portion to loosed the lead strap. In this embodiment, the pawl is constructed and arranged to engage and prevent movement of the lead strap in a direction from the front portion of the housing toward the rear portion of the housing while allowing movement of the strap from the rear portion of the housing to the front portion of the housing.
In one embodiment, the pawl is pivotally mounted to the housing. In a specific implementation, the housing comprises a pressure plate and a pair of substantially parallel side members attached to the pressure plate. The pawl is pivotally mounted between the pair of housing side members such that the second restraining surface is in opposing juxtaposition to the first restraining surface. Generally, the cam buckle includes means for maintaining securely the first retraining surface of the pawl against the first restraining surface of the housing. In the embodiment wherein the pawl is pivotally mounted to the housing, the cam buckle preferably includes a torsion spring disposed about one end of the pivot pin. The torsion spring has a first extension arm in contact with the pawl and a second extension arm in contact with the housing. The torsion spring has a torque sufficient to maintain securely the first retraining surface of the pawl against the first restraining surface of the housing. The first and second restraining surfaces may be any suitable surfaces for retraining the selected type of lead strap. In one preferred embodiment wherein the lead strap is a webbing, the second restraining surface comprises serrations while the first restraining surface comprises grooves.
In another aspect of the invention a cargo retraining device is disclosed. The cargo retraining device includes a lashing strap having a free end and a securable end and a lead strap having a free end and a securable end. A ratchet buckle, interposed between the lashing strap and the lead strap is ratchetably connected to the lashing strap, incrementally tensioning the lashing strap about a cargo load. A cam buckle slidably engages and releases the lead strap. The cam buckle is connected adjacent to the ratchet buckle by an apparatus other than the lead strap and the securing strap.
The ratchet buckle may be any known ratchet buckle suitable for lashing loads. In one embodiment, the ratchet buckle includes a bifurcated frame member having a pair of opposing arms between which a reel member and ratchet wheels are rotatably supported. The ratchet wheels are fixedly attached to the reel member in spaced apart relationship. A latching plate slidably mounted between the frame member arms for latching the ratchet wheels when the ratchet wheels are not being rotatably driven is also included. The lashing strap is wound around the reel member. A lever member is also included in the ratchet buckle. The lever member has a pair of opposing side members rotatably mounted on the reel member. Also included is a ratchet drive plate slidably mounted between the lever member arms for engaging and driving the ratchet it wheel when the lever member is actuated.
In one embodiment, the cam buckle includes a housing and a pawl movably mounted therein. The housing is adapted to slidably receive the lead strap, and has a pressure plate with a first restraining surface over which the lead strap slides. The pawl has a second restraining surface and is biased in an engaged position to restrain the lead strap between the first and second restraining surfaces, thereby preventing movement of the lead strap in a direction that loosens the lead strap while allowing movement of the lead strap in an opposite direction that tensions the lead strap. In one particular embodiment, the housing has a rear portion facing toward the ratchet buckle and a front portion facing away from the ratchet buckle. Passing the lead strap from the front portion to the rear portion of the housing tensions the lead strap and passing the lead strap from the rear portion towards the front portion of the housing loosens the lead strap. The pawl is constructed and arranged to engage and prevent movement of the lead strap in a direction from the front portion of the housing toward the rear portion of the housing while allowing movement of the strap from the rear portion of the housing to the front portion of the housing.
In another embodiment, the cam buckle includes a pawl having a first strap restraining surface and a finger-actuated lever on a side of the pawl opposing the first strap restraining surface, and a pivot pin about which the pawl rotates. A housing defining a second strap restraining surface opposing the first strap restraining surface and having two substantially parallel sides members supporting the pivot pin. A torsion spring, disposed about one end of the pivot pin, has a torque sufficient to maintain securely the first retraining surface of the pawl against the first restraining surface of the housing so as to cause the retraining surfaces to simultaneously contact the lead strap therebetween. This prevents movement of the lead strap in a direction that loosens the lead strap while allowing movement of the lead strap in a direction that tightens the lead strap. Rotation of the pawl lever causes the first retraining surface to rotate away from second retraining surface.
In another aspect of the invention a strap tensioner for tightening and releasing a lashing strap and a lead strap is disclosed. The strap tensioner includes a bifurcated frame member having a pair of opposing parallel arms between which a reel member around which the lashing strap is wound and ratchet wheels are rotatably mounted. A lever member rotatably mounted on the reel member and having a pair of opposing arms between which a ratchet drive plate is slidably mounted for engaging and driving the ratchet wheel when the lever member is actuated. A lead strap pressure plate, mounted between the frame member arms, is constructed and arranged to slidably receive the lead strap. The pressure plate has a first restraining surface over which the lead strap slides. A pawl having a second restraining surface is movably mounted between the opposing arms of the frame member such that the first and second restraining surfaces are in opposed juxtaposition. The pawl is biased such that the first and second restraining surfaces prevent movement of the lead strap in a direction that loosens the lead strap while allowing movement of the lead strap in an opposite direction that tensions the lead strap.
In one embodiment, the pressure plate has a rear end facing toward the ratchet buckle reel and a front end facing away from said ratchet buckle reel, the lead strap traveling from the front end to the rear end of the pressure plate when the lead strap is tensioned, and from the rear end towards the front end of the pressure plate when the lead strap is loosened. The pawl engages and prevents movement of the lead strap in a direction from the front end of the pressure plate toward the rear end of the pressure plate while allowing movement of the strap from the rear end of the pressure plate to the front end of the pressure plate.
In another aspect of the invention, a method for adjusting lead and lashing straps, each secured to a remote object, with a tensioning assembly connected between the lead and lashing straps is disclosed. The method includes (1) passing the lead strap in a tensioning direction through a cam buckle of the assembly. The cam buckle includes a housing having a pressure plate with a first restraining surface on a face thereof. A biased pawl having a second restraining surface movably mounted on the housing such that the first and second restraining surfaces prevent the lead strap from traveling in a loosening direction opposite the tensioning direction. Thus, passing the lead strap in a tensioning direction through a cam buckle of the assembly pre-tensions the lashing strap. The method also includes manipulating a ratchet buckle of the assembly connected adjacent to the cam buckle to incrementally tighten the straps. In certain embodiments the method also includes (3) depressing an extension lever on the pawl to lift the second restraining surface away from the first restraining surface, thereby allowing the lead strap to loosen, removing tension from the lashing strap.
In addition to the above-noted advantages, certain embodiments of the present invention provide additional advantages. For example, the present invention can be handled rapidly, comfortably and safely even by an untrained operator. The invention also enables an operator to quickly release the tensioned load simply by releasing the cam buckle by simple movement of the pawl operating lever to place the pawl in its unengaged position. Furthermore, the tensioning assembly is readily removably or demountable from the object. Also, the present invention enables for the pre-tensioning of a strap in a desired position before securely fastening the strap with the ratchet buckle in a tightened and secured position.
Further features and advantages of the present invention as well as the structure and operation of various embodiments of the present invention are described in detail below with reference to the accompanying drawings. In the drawings, like reference numerals indicate like or functionally similar elements or method steps. Additionally, the left-most one or two digits of a reference numeral identifies the drawing in which the reference numeral first appears.